It has long been known in the disposable absorbent article art that it is extremely desirable to construct absorptive devices, such as disposable diapers, sanitary napkins, incontinent articles, and the like, presenting a dry surface feel to the user to improve wearing comfort and to minimize the development of undesirable skin conditions due to prolonged exposure to moisture absorbed within the article.
One viable prior art solution to the aforementioned problem is disclosed in commonly assigned U.S. Pat. No. 4,342,314 issued to Radel et al. on Aug. 3, 1982 and hereby incorporated herein by reference. Radel et al. discloses an absorbent article with a wearer-contacting topsheet comprising a resilient, macroscopically expanded, three-dimensional plastic web exhibiting a combination of fiber-like and plastic properties. In a preferred embodiment, the macroscopically expanded, three-dimensional plastic web topsheet disclosed in Radel et al. exhibits a fine scale three-dimensional microstructure comprising a regulated continuum of capillary networks, of steadily decreasing size, originating in and extending from one surface of the web and terminating in the form of apertures in the opposite surface thereof to promote rapid fluid transport in the direction of decreasing capillary size. The web's fiber-like appearance is comprised of a continuum of fiber-like elements, the opposed ends of each of the fiber-like elements being interconnected to at least one other of the fiber-like elements.
A typical capillary network in the Radel et al. structure comprises an uppermost capillary opening formed by a multiplicity of primary fiber-like elements interconnected to one another in the uppermost plane of the web. The uppermost opening may, if desired, be further subdivided into smaller capillary openings by secondary and tertiary fiber-like elements at planes located below the wearer-contacting surface of the web.
Each of the fiber-like elements exhibits a substantially uniform U-shaped cross-section along its length. In the case of a primary fiber-like element, its cross-section comprises a base portion located in the wearer-contacting plane and a sidewall portion joined to each edge of the base portion and extending generally in the direction of the absorbent pad-contacting surface of the web. The sidewall portions which intersect one another are joined to one another intermediate the wearer contacting surface and the absorbent pad contacting surface of the web, thereby forming a capillary network interconnecting the opposed surfaces of the web. The secondary and tertiary fiber-like elements, when employed, are generally similar, but originate in planes below the wearer-contacting surface of the web.
One drawback associated with the use of topsheets comprised of plastic is that despite their superior fluid handling characteristics some users are very reluctant to place a topsheet which they readily perceive as plastic by virtue of its glossy appearance in contact with their skin.
To reduce the gloss on the web's visible surface, i.e., that portion of the web which is visible from directly overhead, it has been learned that inclusion of a microscopic pattern of surface aberrations which are not discernible when the perpendicular distance between the viewer's eye and the plane of the web is about twelve inches is highly effective. Commonly assigned U.S. Pat. No. 4,463,045 issued to Ahr et al. on Jul. 31, 1984 and hereby incorporated herein by reference defines the relevant criteria which must be satisfied so that the three-dimensionally expanded web will exhibit a substantially non-glossy visible surface.
A topsheet of the type generally disclosed in Radel et al., having surface aberrations according to Ahr et al., exhibits a fiber-like appearance and tactile impression as well as a non-glossy visible surface. In addition, it is highly effective in promoting rapid fluid transfer from the first wearer contacting surface to the second absorbent pad contacting surface of the topsheet. Topsheets of the latter type have enjoyed widespread commercial success on catamenial pads due to their clean and dry appearance in use when contrasted to conventional nonwoven fibrous topsheets.
Nonetheless, it will be readily appreciated that even further improvement in clean and dry appearance is use are highly desirable in products of this type.
Accordingly, it is an object of the present invention to provide, in a particularly preferred embodiment, a fluid pervious plastic web which retains the foregoing benefits of Radel et al. and Ahr et al., yet which exhibits an even cleaner and drier appearance in use.
It is another object of the present invention to provide, in a particularly preferred embodiment, a fluid pervious plastic web which retains the foregoing but which also exhibits enhanced fluid transfer properties in use.
It is still another object of the present invention to provide, in a particularly preferred embodiment, a fluid pervious plastic web exhibiting a fiber-like appearance and tactile impression, i.e., an overall impression of softness, said web further exhibiting a fine scale three-dimensional microstructure comprising a regulated continuum of capillary networks, preferably of steadily decreasing size originating in and extending from one surface of said film and terminating in the form of apertures in the opposite surface thereof to promote rapid fluid transport in the direction of decreasing capillary size. As utilized herein, the term "microstructure" refers to a structure of such fine scale that its precise detail is readily perceived by the human eye only upon magnification by a microscope or means well known in the art. The term "fiber-like", as utilized herein to describe the appearance of plastic webs of the present invention, refers generally to any fine scale pattern of embossments or apertures, random or nonrandom, reticulated or nonreticulated, which connotes an overall appearance and impression of a woven or nonwoven fibrous web when viewed by the human eye. When describing the elements used to form the web of the present invention, the term "fiber-like" is utilized herein to describe the appearance or shape of the elements. As utilized herein, the term "macroscopically expanded", when used to describe three-dimensional plastic webs, ribbons and films, refers to webs, ribbons and films which have been caused to conform to the surface of a three-dimensional forming structure so that both surfaces thereof exhibit the three-dimensional pattern of said forming structure, said pattern being readily visible to the naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about twelve inches. Such macroscopically expanded webs, ribbons and films are typically caused to conform to the surface of said forming structures by embossing, i.e., when the forming structure exhibits a pattern comprised primarily of male projections, by debossing, i.e., when the forming structure exhibits a pattern comprised primarily of female capillary networks, or by extrusion of a resinous melt directly onto the surface of a forming structure of either type. By way of contrast, the term "planar", when utilized herein to describe plastic webs, ribbons and films, refers to the overall condition of the web, ribbon or film when viewed by the naked eye on a macroscopic scale.